Pulmonary veins carry oxygenated blood from lungs to heart, while pulmonary arteries carry deoxygenated/CO2 rich blood from heart to lungs. On the other hand, systemic arteries carry oxygen-rich blood from the heart to other parts of the body and likewise systemic veins carry CO2-rich blood from all the parts of body back to the heart and lungs. This makes sense to me, since oxygen and CO2 are used and generated in metabolic processes, respectively, and need to be transported to and from the lungs/systemic tissues continuously.
However, what I do not quite understand is what blood vessel carry absorbed nutrients from the intestine to other parts of body? Also, what blood vessels carry other metabolic wastes from the peripheral cells to the kidney for excretion?
Any reference/link to basic working of blood circulation would be helpful.